1. Technical Field
The present invention relates in general to an improved information storage and retrieval disk drive, and in particular to an improved disk stack in a disk drive having reduced disk slippage.
2. Description of the Related Art
Magnetic and optical disk drives are becoming smaller, higher in capacity, and used in more portable applications where they may be subjected to mechanical shock or force. Such shocks can lead to movement or slippage of the magnetic or optical disk that hold information relative to the hub on which they are mounted, resulting in mis-location of pre-written tracks and servo information and further causing mis-located tracks being written to the disk. This in turn can cause failures or degradation of the performance of the disk drive, since the disk's tracks may not be able to be reliably located, followed, and read by the actuator servo system of the disk drive. As disk drives increase in track density and spindle rotation speed, smaller displacements of individual disks or the entire disk stack due to shock induced disk slip will be tolerable before such reliability problems occur.
Disk slip has previously been controlled through application of large normal forces applied to a center region on the surfaces of the disks by a clamp mechanism that holds the disks tightly in position relative to the spindle/hubs and other disks within the disk stack (in large capacity disk drive systems, information is stored on multiple disks configured in what is called a disk stack). Also, disk spacer rings placed between the disks within the disk stack have been fabricated using materials such as ceramics to increase the coefficient of friction between the disks and the spacer rings, thereby resisting disk slippage. An alternative approach that has been used is to adhesively bond a disk to a spindle hub or a spacer, thereby preventing disk slip.
Unfortunately, these prior methods have several disadvantages. The excessive clap loads required to prevent disk slip, as used in the clamping method, often causes distortion of the disks and stripping of clamp screws. The adhesive method creates multiple problems including problems of dispensing the adhesive during manufacture or assembly of the disk drive, and making the disk stack assembly extremely difficult to disassemble for rework and repair. What is needed is a device for preventing disk slip in disk drives that does not apply excessive forces upon the surface of the disks that may cause distortion, that is easily engaged with the disk stack during manufacture or assembly of the disk drive (i.e. does not require the application of a messy adhesive or the addition of a clamping device during assembly), and that can be easily disengaged to allow disassembly of the disk stack during rework or repair.